"Never 10 is an easy to use utility which gives users control over whether their Windows 7 or 8.1 will upgrade itself to Windows 10."

Basically, what Never10 does is to modify the same settings that Microsoft specified would block the Windows 10 upgrade which required the use of Group Policy Editor (gpedit.msc) which is not available to all users--only the Pro and Enterprise versions have gpedit.

According to GRC, Never 10 "...does not install any software of its own. It simply and quickly performs the required system editing for its user."